When Kathryn Sullivan joined the Astronaut Corps in 1978, she was breaking ground for women in space — and luckily she wasn't alone.

“NASA had the wisdom to bring in a critical mass — six women, three African Americans, an Asian,” Sullivan said. “There was a cohort, and we could build a bit of an alliance to tackle some of the issues that come along with adding new people to a close-knit culture.”

That cohort knew the importance of what they were doing.

“All six of us in that first batch of women felt a self-imposed pressure,” she said. “One of us would be the first to fly, another would be the first to do a spacewalk — which only a small group of the Astronaut Corps gets to do. We knew our performance would have a big influence on the prospects of the women who would come after us.”